Easter Island is widely cited as the classic case for unsustainable development, for its Polynesian inhabitants chopped down every single tree, destroying the very means for their own survival.

But a pair of American researchers say it is unfair to portray the Easter Islanders as especially foolish or bent on self-destruction.

Of 69 Pacific islands they surveyed for soil quality, fallout of nutrient-rich volcanic ash and humidity, Easter Island rated the third lowest.

"Easter's collapse was not because its people were especially improvident, but because they faced one of the Pacific's most fragile environments," Barry Rolett and Jared Diamond report in Thursday's issue of Nature, the British weekly science journal.

The Polynesians had fanned out to other islands of the Pacific but, in contrast to Easter, did not carry out the same destruction.

The reason for this, say Rolett and Diamond, is that tree replenishment in those islands, especially those farther north and to the west, was helped by warmer weather and greater humidity.

What may have accelerated Easter's collapse was the local religious cult -- the erection of huge carved stone faces, some of them weighing as much as 60 tonnes, which would required tree felling to make log rollers.

The only islands that rated even lower than Easter for environmental vulnerability were Necker and Nihoa, part of the northwestern Hawaiian islands. Both are treeless.

Easter, one of the most isolated places on the world, lies halfway between Tahiti and Chile.

Archaeological evidence suggests that at its peak, Easter Island's population was more than 10,000.

In its decline, the population plunged into civil war and, apparently cannibalism.

The death knell came with the arrival of Western explorers in the 18th century, which exposed the remaining islanders to disease and slavery. By the end of the 19th century, there were little more than 100 native people left.

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